This is known as an Eulerian frame of reference, and in it at the steady state the time derivatives vanish, as in 30 Computer Modeling of Combustion Reactions Eqs. 21). This reference frame is particularly useful for examination of the properties of steady-state reaction systems such as flames on burners, which are themselves stationary in space. The convection terms remain in the equations. On the other hand, the development of a flame from a localized ignition source is more conveniently studied as a time-dependent phenomenon that eventually reaches a steady propagation rate in space.

22 Computer Modeling of Combustion Reactions 2. Conservation or continuity equations, and other useful relations In order to analyze flames and other reacting systems in terms of basic flow principles and chemical kinetics, it is necessary to consider the conditions in a differential control volume within the reacting fluid. To this control volume we must apply the four fundamental conservation principles which are the basis of all physical and chemical problems: conservation of mass, momentum, energy, and atoms.